Single nucleotide polymorphisms in SEPALLATA 2 underlie fruit length variation in cucurbits

Area of Science:

• Plant genetics and breeding
• Molecular biology
• Agricultural science

Background:

• Complete gene disruption often leads to detrimental growth defects, limiting crop breeding applications.
• Identifying subtle genetic variations, such as single-nucleotide polymorphisms (SNPs), is crucial for targeted trait improvement in crops.

Purpose of the Study:

• To investigate the role of single-nucleotide polymorphisms (SNPs) in the cucumber SEPALLATA2 (CsSEP2) gene in regulating fruit length.
• To explore the potential of utilizing subtle genetic variations in essential genes for crop breeding.

Main Methods:

• Identified two SNPs in the CsSEP2 gene associated with fruit length variation in natural and mutagenized cucumber populations.
• Phenotypically characterized near-isogenic and mutant lines to assess the impact of different CsSEP2 haplotypes on fruit length.
• Analyzed the regulatory mechanism involving CsSEP2, CRABS CLAW (CsCRC) transcription, and cell expansion.

Main Results:

• Two natural haplotypes (HAP1, HAP2) and one induced haplotype (HAP3) of CsSEP2 were identified, showing significant differences in fruit length.
• Fruit length increased from HAP1 to HAP2 and further in HAP3, correlated with reduced CsCRC transcription and enhanced cell expansion.
• A conserved SEP2-CRC module regulating fruit length was also observed in melon (Cucumis melo).

Conclusions:

• Subtle SNPs in the CsSEP2 gene specifically modulate cucumber fruit length by affecting the CsCRC regulatory pathway.
• This study provides a valuable strategy for leveraging essential genes with pleiotropic effects in crop improvement programs.